Tens of thousands of gay men who were persecuted and murdered by the Nazi regime are remembered in a memorial unveiled yesterday in central Berlin.

A grey concrete pillar, encompassing a small slanted window displaying a film of two men locked in a passionate kiss, is the first national monument of its kind, and was constructed only after decades of debate about how to mark the crimes perpetrated against Germany's gay population.

"Germany wants to honour the persecuted and murdered victims, to keep alive the memory of the injustice they suffered," a plaque reads, adding that the monument is meant as "a lasting symbol against intolerance and hostility towards gays and lesbians and against their alienation".

But gay rights campaigners, while welcoming the memorial, said it was an unfortunate consequence of the lengthy struggle to see it constructed, that there were no survivors left to witness its inauguration.

"It is a sad fact that not one of the people persecuted back then is able to be here today," said Günter Dworek, a spokesman for Germany's Lesbian and Gay Association. "In that sense, this monument has come too late." The last known victim died in 2005.

Nazi Germany's open policy against homosexuality began in 1933 when officials ordered the destruction of the Berlin institute of the sexologist and physician, Magnus Hirschfeld. Between 1935 and 1945 more than 50,000 men were convicted. It is estimated that between 5,000 and 15,000 of them were sent to concentration camps.

In some cases gay men, who were forced to wear pink triangles, were sterilised or used as medical guinea pigs. Precise figures of how many died in death camps are unknown, but the figure is estimated to be in the thousands.

Unlike other groups of Nazi victims, the gay community was largely ignored after the collapse of the Third Reich. Worse still, they continued to be persecuted by the same law until 1969, which saw a further 50,000 sentenced for the crime of being gay. It was not until 2002 that they were pardoned by the Social Democrat-Green coalition government, which also abolished the legislation. Campaigners are still fighting for compensation for many of those who fell victim to the law.

In 2003 the government announced a competition for a memorial in Tiergarten park, which was won by the Berlin-based artists Michael Elmgreen and Ingar Dragset, who incorporated the one and a half minute kissing film loop by director Thomas Vinterberg into their design.